Electron discharge device with planar electrodes



E. B. GEMPLER ETAL 3,207,940

2 Sheets-Sheet l INVENTORSZ EDWARD B. GEMPLER ROBERT WATSON, B WM THElR ATTQRNE Sept. 21, 1965 ELECTRON DISCHARGE DEVICE WITH PLANAR ELECTRODES Filed March 9, 1960 Sept. 21, 1965 E. B. GEMPLER ETAL 3,207,940

ELECTRON DISCHARGE DEVICE WITH PLANAR ELECTRODES Filed March 9, 1960 2 Sheets-Sheet 2 FIG.2.

INVENTORSZ EDWARD B.GEMPLER, ROBERT R. WATSON BYVMY- g THEIR ATTORNE United States Patent 3,207,940 ELECTRON DISCHARGE DEVICE WITH PLANAR ELECTRODES Edward B. Gempler, Scotia, and Robert P. Watson,

Schenectady, N.Y., assignors to General Electric Company, a corporation of New York Filed Mar. 9, 1969, Ser. No. 13,899 14 Claims. (Cl. 313-256) Our invention relates to electric discharge devices and pertains more particularly to improvements in the electrode arrangements in high frequency electron tubes of the planar electrode types.

Some high frequency electron tubes of the planar electrode types include an anode assembly comprising a cupshaped anode shell bonded to one end of an insulator. The shell generally carries a metal anode slug, the transverse inner end of which extends reentrantly in the insulator and serves as a planar active anode surface for cooperating electrically with planar grid and cathode elements in the tube. The slug is usually formed with an exhaust passage extending therethrough and carries an exhaust tubulation for effecting a seal following exhaust of the tube. Additionally, the outer end of the slug and the tube are usually fitted with a heat radiator for dissipating heat from the anode.

In tubes of the above-described type it is sometimes desirable to decrease the grid-anode inductance in order thereby, for example, to vary the tuning range curve or, in other words, the plot of the grid-anode cold resonant frequency against the grid-anode capacitance. Additionally, it is generally desirable to increase power output of such a device. Further, it is generally desirable to provide for increased mechanical strength of the mounting means for the anode slug and radiator to insure concentricity of the slug and parallelism of its active inner end relative to the other planar electrodes in the tube, especially in view of the extremely close interelectrode spacing usually required in high frequency devices of this type.

Accordingly, a primary object of our invention is to provide a new and improved high frequency electric discharge device including improved means for decreasing the grid-anode inductance.

Another object of our invention is to provide an improved electric discharge device including improved means for reducing capacitance between the grid and anode, thereby to enable closer spacing of these electrodes for affording increased power output at high frequency operation.

Another object of our invention is to provide a new and improved electric discharge device including improved means adapted for both decreasing the grid-anode inductance and increasing the mechanical rigidity of the anode slug in the assembly.

Another object of our invention is to provide improved means for aifording the desired effects on the grid-anode inductance and capacitance, which is simple in construction and which can be easily and inexpensively incorporated in presently available planar electrode tube constructions to adapt them for operating capabilities not heretofore attainable.

Further objects and advantages of our invention will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of our invention we provide an electron tube including a conductive cup-shaped anode shell bonded to one end of a cylindrical ceramic insulator. Bonded to the opposite end of the insulator are cathode and grid assemblies wherein planar cathode and grid electrodes are mounted in closely spaced parallel relation. Mounted concentrically in the anode shell is a metal anode slug. The anode slug includes a shank portion and an enlarged head portion. The end of the slug carrying the head extends reentrantly in the insulator and the head is provided with a planar active surface in closely spaced parallel relation to the grid. The slug is provided with an exhaust passage which communicates with the interior of the tube. Additionally, the side of the head is predeterminedly chamfered to provide a predetermined effect on the grid-anode capacitance. The grid-anode inductance is predeterminedly affected by means which increases the effective diameter of the reentrant portion of the anode slug. Additionally, the last-mentioned means is effective for rigidizing the mounting of the reentrant portion of the anode slug and, in some forms of the invention, is also effective for increasing the heat conducting paths away from the head portion of the anode.

For a better understanding of our invention reference may be had to the accompanying drawing in which:

FIGURE 1 is an enlarged partially sectionalized view illustrating a preferred embodiment of our invention;

FIGURE 2 is an enlarged fragmentary sectional view illustrating a modified form of our invention; and

FIGURE 3 is an enlarged fragmentary sectional view illustrating another modified form of our invention.

Referring to the drawing, there is shown in FIGURE 1 a high frequency electric discharge device of a planar electrode type including a hermetically sealed envelope generally designated 1. The envelope comprises several stacked metallic and insulative members including a straight cylindrical ceramic insulator 2. Sealed to the lower end of the insulator 2 is an annular metal contact 3. Extending concentrically in the contact 3 is an annular contact 4. The contacts 3 and 4 comprise wall portions of the envelope and are mutually insulated by suitable ceramic members. Suitably mounted in the envelope in predetermined closely spaced relation are planar grid and cathode electrodes 5 and 6, respectively. The contact 3 is adapted for making an electrical connection to the grid 5. The contact 4 and another contact are adapted for making electrical connections to the cathode 6 and a filamentary heater therefor. In view of the fact that the present invention does not involve the lower end of the device, several of the elements referred to in connection with the lower end of the envelope have not been shown in the drawing.

To the upper end of the insulator 2 is sealed a conductive anode shell generally designated 7. The shell 7 can be satisfactorily formed of copper-clad chrome iron and is generally cup-like in configuration. The shell 7 includes a generally planar bottom surface 8, an elongated cylindrical inner portion or neck 9 extending reentnantly in the insulator 2 and a cylindrical outer portion 19 which embraces the upper end of the insulator 2 and is suitably hermetically sealed thereto. Extending upwardly from portion 10 is another cylindrical portion 11 which serves as an annular anode contact.

Fitted and bonded in the cylindrical neck 9 of the shell is a copper anode slug generally designated 12. The slug 12 includes a cylindrical shank 13 and an enlarged head portion 14. The head 14 includes a back surface 15 which is engaged by the inner edge of the neck 9 of the shell. Additionally, the head 14 can be provided with a transversely extending exhaust passage 16 which opens on both sides of the head and communicates with a vertical passage 17 extending coaxially through the shank 13. Alternatively, the exhaust passage can extend through the active end surface of the anode.

Bonded in the upper end of the exhaust passage 17 is a metal exhaust tubulation 18. The tubulation 18 includes radiator rests on the bottom surface of the shell, which serves to assist in rigidizing the mounting of the radiator 20 and the anode slug fitted 12 therein.

The anode head 14 includes a planar transverse active end surface 23 which is normally parallel to and closely spaced from the planar grid electrode 5. In the abovedescribed arrangement the elongated neck 9 of the shell embraces the shank of the anode slug for a considerable length of the shank and thereby assists in rigidizing the mounting of the anode slug such as to insure against tilting of the anode-radiator arrangement. This serves to insure the desired parallelism and close spacing of the anode active surface 23 relative to the inner grid 5.

Additionally, the anode head 14 is chamfered or tapered fully from the back surface 15 to the active surface 23 to provide a predetermined frusto-conical side surface 24. This chamfered or tapered surface is such that the active area 23 is smaller than the area of the electron-permeable portion of the grid or, expressed in another manper, the diameter of the circular active area 23 of the anode head is smaller than that of the area of the circular mesh or electron permeable portion of the grid 5. We have found that this arrangement can be obtained satisfactorily when the largest diameter of the head is approximately that of the mesh or electron permeable portion of the grid and when the head is chamfered or tapered at an angle of approximately 75 degrees from the planar active surface 23. We have also found that this arrangement reduces the direct and fringe capacitance between the grid and anode and allows these electrodes to be more closely spaced, with the highly desirable result of adapting the device for higher power output. For example, in some devices it has been possible with the present structure to decrease the spacing between the grid and anode active surfaces by approximately .010 inch to .012 inch, thereby to provide a grid-to-anode spacing of approximately .020 inch for the purpose of substantially increasing the power output of the tube. With our invention, increases in power output as much as 25% to 40% at high frequency operation have been obtained, and while still maintaining other desired electrical characteristics. Such power increases are not possible with prior art structures where the anode head is-not predeterminedly shaped to reduce the planar active area of the anode seen by electrons passing through the grid. In structures not including an anode head shaped according to the present invention the direct fringe capacitance between the grid and anode would be such as to preclude the closer spacing of these electrodes and, thus, would be ineffective for increased power output without adversely affecting other desired electrical characteristics.

Additionally, for some applications of the described type of tube it is desirable to decrease the electrical inductance of the grid-anode portion of the tube, for example, to obtain a more satisfactory plot of grid-anode cold resonant frequency versus grid-anode capacitance. We have found that the grid-anode inductance can be decreased effectively and without substantial changes in the basic tube arrangement by providing means effective for increasing the effective diameter of the reentrant portion of the anode. Expressed in another manner, the structure of the present invention affords a conductive low R.F. (radio frequency) loss surface which commences at the back surface of the anode head, extends radially outwardly toward the inner wall of the insulator 2 and continues as a conductive surface extending upwardly to the end of the insulator and making electrical contact with the bottom surface 8 of the anode shell 7.

Illustrated in FIGURE 1 is a preferred form of structure adapted for providing the desired conductive surface effective for decreasing the grid-anode inductance. This form of our invention involves the provision of a thin- Walled cup-shaped element 25, which can be formed of copper, nickel-iron alloy or any other suitable material or coated material for affording low R.F. losses. The element 25 includes an apert-ured bottom, the edge of which is bonded to the back surface 15 of the head 14 and the inner end of the shell neck 9. The side wall of the element 25 extends in closely spaced parallel relation to the inner wall of the straight insulator 2, and the rim of the element 25 is bonded to the inner surface of the shell bottom 8. In this .arrangement the element 25 is effective for both reducing substantially the grid-anode inductance and is further effective for serving as an internal brace for assisting in rigidizing the mounting of the anode slug to insure against tilting thereof and the adverse effects on the parallelism of the grid and anode could result from tilting of the slug. Still further, the member 25 increases the heat conductivity to the external portions of the anode shell for dissipation thereby.

Illustrated in FIGURE 2 is a modified form of structure adapted for reducing the grid-anode inductance by increasing the effective diameter of the reentrant portion of the anode. This form involves the provision of a thickwalled cylinder 26 formed of a material affording a low R.F. loss surface. The inner diameter of the cylinder 26 is such as to fit tightly over the neck 9 of the anode shell and the outer diameter is such as to dispose the cylindrical outer surface of the member 26 in close proximity to the wall of the insulator 2. The cylinder 26 is formed to a length suflicient to extend from the back surface 15 of the anode head 14 to the bottom surface 8 of the shell. In all other respects the tube structure can be identical and elements comparable to those shown in the structure of FIGURE 1 are designated with identical numerals.

In FIGURE 3 is illustrated another modified form of our invention including structure adapted for reducing the grid-anode inductance by increasing the effective diameter of the reentrant portion of theanode. In this form the anode shell 7 is drawn to include a reentrant and cup-like inner portion 27 which extends downwardly t0 the back surface 15 of the head 14 of the anode and is of such diameter as to dispose the cylindrical wall thereof in close proximity to the wall of the insulator 2. More specifically, the reentrant portion 27 of the shell includes an apertured planar bottom 28 which receives the shank of the anode slug and is bonded to the shank and the surface 15 behind the head of the anode. The bottom 28 is of such diameter as to extend close to the inner wall of the insulator 2 and a straight cylindrical side wall portion 29 extends in closely spaced parallel relation to the inner wall of the insulator 2. This structure is also effective for bracing the inner end of the reentrant anode to rigidize the anode structure against tilting. Otherwise, the structure in FIGURE 3 can be identical to that of FIG- URES l and 2 like numerals identify like elements. Additionally, the member 7 is preferably formed of a material to afford a low R.F. loss surface on the portion 27.

It will be seen that the structure of FIGURES 1 and 2 are particularly attractive from the manufacturing standpoint in view of the fact that they require parts which can be formed by means of relatively simple drawing operations. Additionally, these forms of the invention are particularly attractive in that they involve the use of thin-walled elements and thus will not tend to introduce stresses which might adversely affect the ceramicto-metal seals between the anode shell and the insulator 2.

While we have shown and described specific embodiments of our invention we do not desire our invention to be limited to the particular forms shown and described,

and we intend by the appended claims to cover all modifications within the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge device comprising an envelope including a cylindrical insulator, planar cathode and grid electrodes supported in the lower end of said insulator, a conductive anode contact member across the upper end of said insulator, an anode slug bonded centrally in said contact member and extending therethrough reentrantly in said insulator, the inner end of said slug defining a planar active surface in closely spaced parallel relation with said grid electrode, and means extending the effective diameter of the reentrant portion of said anode slug to a point adjacent the inner Wall surface of said insulator for decreasing the grid-anode inductance of said device.

2. An electric discharge device comprising an envelope including a cylindrical insulator, planar cathode and grid electrodes supported in the lower end of said insulator, a conductive anode shell bonded to the upper end of said insulator, an anode slug bonded centrally in said shell and extending therethrough reentrantly in said insulator, the inner end of said slug defining a planar active surface in closely spaced parallel relation with said grid electrode, and means providing a low R.F. loss conductive surface commencing behind said active surface of said anode, extending radially outwardly toward said insulator and extending to the upper end of said insulator and in close proximity to the wall of said insulator, thereby to increase the effective diameter of the reentrant portion of the said anode for decreasing the grid-anode inductance of said device.

3. An electric discharge device comprising an envelope including a cylindrical insulator, planar cathode and grid electrodes supported in the lower end of said insui-ator, a conductive anode shell bonded to the upper end of said insulator, an anode slug bonded cent-rally in said shell and including a shank and an enlarged head portion extending reentrantly in said insulator, the end of said head defining a planar active surface in closely spaced parallel relation with said grid electrode, and means providing a low R.F. loss conductive surface commencing behind said head portion, extending radially outwardly toward said insulator and extending to the upper end of said insulator in closely spaced relation to the inner wall of said insulator, thereby to increase the effective diameter of the reentrant portion of said anode for decreasing the grid-anode inductance of said device.

4. An electric discharge device comprising an envelope, planar cathode and grid electrodes supported in said envelope from one end of said envelope, said grid electrode having an electron-permeable part of predetermined cross-sectional area, an anode slug extending reentrantly in the opposite end of said envelope, said slug including an enlarged head portion of cross section substantially equal to said electron-permeable part of said grid, and said head portion being tapered toward said grid to define an active anode surface of lesser area than said grid electrode, thereby to reduce the grid-anode capacitance of said device.

5. An electric discharge device according to claim 4, wherein the taper on said anode head is provided by an annular chamfer of approximately 75 degrees from the plane of said active anode surface.

6. An electric discharge device according to claim 3, wherein said anode head is tapered toward said grid and thereby provides a planar active surface of lesser area than said grid, whereby the grid-anode capacitance of said device is decreased.

7. An electric discharge device comprising an envelope including a cylindrical insulator, planar cathode and grid electrodes supported in the lower end on said insulator, a conductive anode shell having a transverse surface bonded to the upper end of said insulator, an enlongated cylindrical portion of said shell extending reentrantly in said insulator, an anode slug including a shank and an enlarged head portion having a transverse planar end surface extending parallel to said grid, said shank being bonded in said cylindrical portion of said shell, and a thin-walled cup-like conductive element including a low R.F. loss inner surface and an apertured bottom fitted about said anode slug just behind said head and including a straight cylindrical wall portion extending upwardly to said transverse end of said shell and in close proximity to the wall of said insulator, thereby to increase the effective diameter of the reentrant portion of said anode for decreasing the grid-anode inductance of said device.

8. An electric discharge device according to claim 7, wherein said enlarged head portion is tapered toward said grid and the diameter of said grid is greater than the diameter of the active surface of said anode, whereby grid-anode capacitance of said device is decreased.

9. An electric discharge device comprising an envelope including a ceramic insulator, planar cathode and grid electrodes supported in the lower end of said insulator, a conductive anode shell having a transverse surface bonded to the upper end of said insulator, an elongated cylindrical portion of said shell extending reentrantly in said insulator, an anode slug including a shank and an enlarged head portion having a transverse planar end surface extending parallel to said grid, said shank being bonded in said cylindrical portion of said shell, and a thick-walled conductive member having a low R.F. loss surface fitted about said shank and extending from said transverse surface of said shell to just behind said head and including a straight cylindrical outer surface extending in closely spaced parallel relation to the inner wall of said insulator, thereby to increase the effective diameter of the reentrant pontion of said anode for decreasing the grid-anode inductance of said device.

10. An electric discharge device according to .claim 9, wherein said enlarged head is tapered toward said grid and the diameter of said grid is greater than the diameter of the active surface of said anode, whereby grid-anode capacitance of said device is decreased.

11. An electric discharge device comprising an envelope including a cylindrical insulator, planar cathode and grid electrodes supported in the lower end of said insulator, a conductive anode shell having a transverse surface bonded to said upper end f said insulator, and a thin-walled cup-like portion having a low R.F. loss surface and extending reentrantly in said insulator, said cup-like portion including a cylindrical wall extending in close parallel relation to the wall of said insulator, and an apertured bottom wall, an anode slug including a shank and an enlarged head portion having a transverse planar end surface extending parallel to said grid, and said shank being bonded to the rim of the apertured bottom of the said cup-like portion just behind the head portion, whereby the etfective diameter of the reentrant portion of said anode is increased for decreasing the grid-anode inductance of said device.

12. An electric discharge device according to claim 11, wherein said enlarged head is tapered toward said grid and the diameter of said grid is greater than the diameter of the active surface of said anode, whereby the gridanode capacitance of said device is decreased.

13. An electron discharge device, comprising an envelope including a tubular insulator, spaced cathode and grid electrodes supported in mutually parallel relationship in one end of said insulator, an anode supported from the other end of said insulator and extending reentrantly therein, the inner end of said anode defining an active surface in closely spaced parallel relationship to said grid electrode, said anode including a portion having an effective average diameter greater than that of the active surface and slightly less than that of the diameter of the bore of said insulator, whereby the grid-anode inductance of said device is effectively reduced.

14. An electric discharge device, comprising an envelope, cathode and grid electrodes supported in said envelope from one end thereof, an anode extending re- 7 8 entrantly in the opposite end of said envelope, said anode 2,446,269 8/48 Drieschrnan 313265 including an enlarged portion having an active end sur- 2,507,972 5/50 Haeff 313249 X face extending parallel to said grid electrode, said end "2,644,907 7/53 Drieschman et al. 313270 X portion-being tapered toward said grid to define an area 2,655,614 10/53 Doolittle et a1. 313-249 less than that of said grid electrode thereby effectively to 5 2,722,624 11/55 Doolittle 313250 reduce the grid-anode capacitance of said device. 2,819,421 1/58 Ringland et a1. 3l3146' References Cited y the Examiner JOHN W. HUCKERT, Primary Examiner.

UNITED STATES PATENTS ARTHUR GAUSS, RALPH G. NILSON, Examiners.

2,402,602 6/46 Chevigny 313-246 X 

1. AN ELECTRIC DISCHARGE DEVICE COMPRISING AN ENVELOPE INCLUDING A CYLINDRICAL INSULATOR, PLANAR CATHODE AND GRID ELECTRODES SUPPORTED IN THE LOWER END OF SAID INSULATOR, A CONDUCTIVE ANODE CONTACT MEMBER ACROSS THE UPPER END OF SAID INSULATOR, AN ANODE SLUG BONDED CENTRALLY IN SAID CONTACT MEMBR AND EXTENDING THERETHROUGH REENTRANTLY IN SAID INSULATOR, THE INNER END OF SAID SLUG DEFINING A PLANAR ACTIVE SURFACE IN CLOSELY SPACED PARALLEL RELATION WITH SAID GIRD ELECTRODE, AND MEANS EXTENDING THE EFFECTIVE DIAMETER OF THE REENTRANT PORTION OF SAID ANODE SLUG TO POINT ADJACENT THE INNER WALL SURFACE OF SAID INSULATOR FOR DECREASING THE GRID-ANODE INDUCTANCE OF SAID DEVICE.
 4. AN ELECTRIC DISCHARGE DEVICE COMPRISING AN ELVELOPE, PLANAR CATHODE AND GRID ELECTRODES SUPPORTED IN SAID ENVELOPE FROM ONE END OF SAID ENVELOPE, SAID GRID ELECTRODE HAVING AN ELECTRON-PERMEABLE PART OF PREDETERMINED CROSS-SECTIONAL AREA, AN ANODE SLUG EXTENDING REENTRANTLY IN THE OPPOSITE END OF SAID ENVELOPE, SAID SLUG INCLUDING AN ENLARGED HEAD PORTION OF CROSS SECTION SUBSTANTIALLY EQUAL TO SAID ELECTRON-PERMEABLE PART OF SAID GRID, AND SAID HEAD PORTION BEING TAPERED TOWARD SAID GRID TO DEFINE AN ACTIVE ANODE SURFACE OF LESSER AREA THAN SAID GRID ELECTRODE, THEREBY TO REDUCE THE GRID-ANODE CAPACITANCE OF SAID DEVICE. 